Defect Complexes and Optical Properties of Doubly Doped Lithium Niobate Crystals

Abstract

The effect of defect complexes related to the presence of protons on the optical properties of LiNbO₃:Y(0.24):Mg(0.63) and LiNbO₃:Gd(0.25):Mg(0.75) (wt %) crystals has been studied using IR absorption spectroscopy, photoinduced light scattering, and laser conoscopy. The results indicate that the absorption bands at frequencies of 3483 and 3486 cm^–1 correspond to vibrations of a V_Li^-–OH⁻ defect complex. To a Mg _Li⁺ - Mg _Nb^3-–OH⁻defect complex in the LiNbO₃:Gd(0.25):Mg(0.75) crystal correspond bands at frequencies of 3526 and 3535 cm^–1. In the LiNbO₃:Y(0.24):Mg(0.63) crystal, we have detected an anomalous opening of the speckle structure of the photoinduced light scattering indicatrix.